1. Field of the invention
The invention relates to a transmission mechanism and, more particularly to a transmission mechanism capable of changing an angle of an optical element.
2. Description of the Related Art
In a variable optical attenuator (VOA) or a tunable filter, a transmission mechanism is often used to adjust the inclined angle of an optical element such as a flat glass or a filter so as to obtain different refracting offsets or wavelengths.
Referring to FIG. 1, a conventional transmission mechanism 2 includes a lead screw 203, a moving member 204 and an arm 205. The lead screw 203 is driven by a stepping motor 201 so that the lead screw 203 moves by way of its threads. As shown in FIG. 2, since the moving member 204 is telescoped onto the lead screw 203, the moving member 204 also moves on the base 202 when the stepping motor 201 drives the lead screw 203 to move. In addition, a roller 214 is provided at one end of the moving member 204, a slot 215 is formed in the arm 205, and the roller 214 can slide back and forth along the slot 215. Therefore, when the moving member 204 moves, the roller 214 at one end of the moving member 204 slides along the slot 215 so as to rotate the arm 205. Accordingly, the filter 3 connecting to one end of the arm 205 also rotates. When the filter 3 rotates to a specified angle, the light having a different central wavelength output from the collimators 4 can be filtered due to the angle variation of the filter 3.
If the arm is made longer, the angle variation of the optical element such as a filter becomes smaller. That is, it is possible to finely adjust the transmission mechanism so as to improve the resolution thereof. However, when the arm is made longer, the volume of the transmission mechanism is also greater. In this case, such optical products cannot meet the requirement of light, thin, short and small tendency.
Although the pitch of the lead screw can be decreased to shorten the moving distance of the moving member and reduce the angle variation of the optical element, this way will greatly increase the manufacturing difficulty and the manufacturing costs.
Accordingly, it is an important subject of the invention to increase the resolution of the transmission mechanism and decrease the volume thereof.
In view of the above-mentioned subject, it is therefore an objective of the invention to provide a transmission mechanism with a high resolution and a small volume.
To achieve the above-mentioned objective, the transmission mechanism of the invention is provided in an optical device for changing an angle of an optical element. The transmission mechanism includes a first member and a second member. The first member has a slanted surface and is capable of sliding back and forth along a first direction. An angle between a normal direction of the slanted surface and the first direction is constant and not a 90-degree angle. The second member has a first part and a second part. The first part is contacted with the slanted surface of the first member. The second part is connected to the optical element. When the first member moves, the first part contacting the slanted surface moves relative to the slanted surface, thereby causing the second part to rotate so as to change the angle of the optical element.
When the first member moves, the first part of the second member moves relative to the slanted surface so as to change the angle of the optical element. On the basis of the geometric relationship between the first member and the second member, the minimum rotation angle of the optical element can be made very small. That is, it is possible to finely adjust the optical element so as to increase the resolution of the transmission mechanism and to greatly reduce the overall volume of the transmission mechanism.